The Echinoid Directory

Order Arbacioida Gregory, 1900, p. 307

[ex Arbacina Gregory, 1900, p. 307]

Diagnosis Echinacea with:
  • apical disc small (much smaller than the peristome), dicyclic (rarely hemicyclic); periproct margin smoothly rounded; enclosing periproct
  • ambulacra and interambulacral tubercles small and similar in size; imperforate and non-crenulate in all but the basalmost members;
  • plate compounding in arbaciid or goniopygid style, with at least one demiplate;
  • Basicoronal plate present in interambulacral zones.
Range Middle Jurassic to Recent, worldwide.
Type Arbacia
Species Included This order includes the following families: Acropeltidae, Arbaciidae and Glypticidae.  There are also a number of primitive genera that probably belong here as they have a single large basicoronal plate to interambulacral zones (Dubarechinus, Magnosia, Eucosmus).
Classification and/or Status Euechinoidea, Acroechinoidea, Carinacea, Echinacea

The order is distinguished from other Echinacea by its retention of a basicoronal plate in interambulacral zones and in by its characteristic plate compounding. It includes Eucosmechinae Lambert & Thiery, 1911, p. 269.

Gregory, J. W. 1900. The Echinoidea, in E. R. Lankester (ed.) A Treatise on Zoology. Part III, the Echinodermata. Adam & Charles Black, London.